Brum Brum Brum

[Big Sugar]

Ok guys

I'm getting a Brum Brum Brum resonation at high speeds like 70 mph + then i need to slow down to 50 to clear it out? At first i thought it was the pavement but the tonight i noticed it again.. Rear tires are new no noticible vibration in the car mirrors are steady ('cept for my centre rear view @$#]*=* self adjusting).
U joints are ok  and no noticible hum or Brumming below the 55 mph mark ?

Any ideas ? Rear axle ? Driveshaft ? body in the trunk ? Too much downforce from my hemi spoiler throwing off my pinion angle ? Or am I simply driving to fast for my own good...maybe its those front drums warning me ?


Ron

[cdr]

I WOULD BET driveshaft

[heyoldguy]

Did this just start happening?

[Chryco Psycho]

When did it start ? BFJunk tires ??

[XH29N0G]

I would check tire balance, but that said, I had a driveline vibration related to the driveshaft and it seemed to just appear. 

In my case it felt like I hit rumble strips at a certain speed and continues whether or not the clutch was engaged.  It stopped when I slowed and resumed shortly after I hit that speed again.

Someone suggested having someone in the back seat see if the vibration came from the middle or one side as part of the diagnosis. 

[Big Sugar]

Tires are new out back and they are bfg's but the symptoms go back to before the tire change



Ron

[Chryco Psycho]

Trans mount , tailshaft bushing , Pinion angle , bad U joint ,bad axle brg ...
I would still check the tires closely for steps in the tread etc , I have seen brand new tires with 3/8" step where the belts overlap .

[RallyeMike]

In my experience if it is harmonic (brum, brum, brum a good description) , it is most likely not tires, more likely drive shaft related (balance, angles, trans mount, u-joint).

[mvandale]

An quite rare (but frustrating) thing happened to me like that once & it turned out to be the tailshaft (in trans) bushing.  Never heard of that thing before, but lo and behold, it is a metal sleeve that keeps the tailshaft yoke from wobbling and certain speeds. 

Again, I wouldn't replace that as a first-option (tires, balancer, driveshaft, etc.) are all more likely, just wanted to say that weird parts fail too!

[Big Sugar]

Well  the U joints are the smaller ones and they feel Ok so i'll start be checking out the driveshaft and tailshaft bushing,  im wondering if it might just be worth it to upgrade the driveshaft and go with the larger U joints and just save the hassle later, whats a driveshaft go for with the larger yokes nd U joints.
Any good places to shop for one ?


Ron

[cdr]

did you remove the shaft to check the joints

[Paul G]

Is the original drive train still in the car?

[Big Sugar]

did you remove the shaft to check the joints

No not yet ? Should i pull the shaft then .......?....ok let me refrase that.......should i remove the driveshaft and then check the U joints ?.

Is the original drive train still in the car?

No.. It was a 361 car now we have a440 6 pak different rear end and tranny as well.



Ron

[Paul G]

Since the drive train is not original to the car I really suspect drive train alignment, which becomes pinion angle problems at the drive shaft. There is a lot of info about it on this board, use search, as well as Google searching. is the trans tail shaft sitting in the correct spot between the sub frame rails? Mopar engines sit off center to the passenger side. Is the trans tail shaft and the pinion on the diff angled correctly to each other?

[cdr]

yes remove & make sure the joints move very easy in all directions,also look for dented driveshaft,check at rear yoke that the ujoint fits tight against the c clips on the ujoint caps http://www.driveshaftspecialist.com/PDF/Pinion%20Yoke-No%20Tabs%20FORM.pdf